The present invention relates generally to the field of infusion pumps and, more particularly, to a disposable, non-gravity fed, elastomeric infusion pump used to infuse fluids intravenously to a patient without dependence on gravity.
It is often necessary to supply patients intravenously with pharmaceutically active liquids over a long period of time at a controlled rate. It is desirable that this is accomplished while the patient is ambulatory.
Previous devices, such as those described in U.S. Pat. Nos. 5,080,652 and 5,105,983 to Sancoff et al., include elastomeric bladders which, when filled, create pressure to pump the infusor liquid to a patient. These devices, however, are inadequate because they deliver high amounts of fluid at the outset of infusion (40% of fluid in first 25% of time) followed by lower amounts later. Further, these devices result in reduced pressure within the bladder at the terminal end of the infusion cycle, which may result in backflow of infusor liquid into the device from the patient.
U.S. Pat. Nos. 4,915,693 and 4,769,008 to Hessel relate to elastomeric bladder pumps which prestetch the bladder over a stress member both axially and radially, which provides a somewhat more constant pressure profile throughout the cycle. However these devices operate to eliminate the pressure surge within the bladder at the terminal end of the infusion cycle, which may result in backflow of infusor liquid and blood from the patient into the device. Further, prestretching the bladder in both the axial and radial directions requires numerous clamps and other elements, resulting in increased cost and complexity. In addition, because of the need to maintain the chemical integraty of the infusor liquid, these devices are limited in the material which may be used as the bladder. Also, these devices do not include an easy means for sealing the open end of the bladder in a way which does not require clamps and other complicated seals.
The present invention is directed to overcoming these deficiencies.
With parenthetical reference to the corresponding parts, portions or surfaces of the disclosed embodiment, merely for the purposes of illustration and not by way of limitation, the present invention provides an improved infusion pump (15) for delivering a quantity of liquid at a substantially constant flow rate, the infusion pump having an elastomeric hollow balloon (140) and a longitudinal member (110), the balloon having an axial and radial dimension and an open end (22), the longitudinal member having an insertion member (16) extending into the hollow portion (24) of the balloon. The improvement comprises the insertion member and the balloon being so configured that the insertion member stretches the elastomeric balloon in the radial direction, but does not stretch the balloon in an axial direction, whereby the infusion pump delivers the quantity of liquid at a substantially constant flow rate.
The present invention also discloses an infusion pump for delivering a quantity of liquid at a substantially constant flow rate, the pump having an elastomeric hollow balloon and an insertion member, said balloon having an axial and radial dimension and an open end. The improvement comprises a hollow inert membrane (130), the insertion member extending into the hollow portion (23) of the membrane, and the insertion member and the membrane extending into the hollow portion of the balloon, such that the membrane is between the insertion member and the balloon.
The insertion member may comprise an upper portion (18) and a lower portion (19), the upper portion having an upper outside diameter (25) and the lower portion having a lower outside diameter (26), the upper and lower diameters being different. The upper diameter may be greater than the lower diameter. The upper diameter may be about 1.3 to 1.6 times the unstretched inner diameter of the balloon and the lower diameter may be about 1.0 to 1.2 times the unstretched inner diameter of the balloon.
The infusion pump may include a shell. The pump may comprise a shell which includes a bearing surface (21), a longitudinal member which includes a cap section (17), the cap section including a cap bearing surface (20), wherein the cap bearing surface and shell bearing surface are so configured as to seal the open end of the balloon when the shell and the cap section are connected.
Accordingly, the general object of the present invention is to provide a infusion pump which is capable of supplying pharmaceutically active liquids over an extended period of time at a controlled rate.
Another object is to provide an infusion pump with a balloon sealing mechanism which is cost effective and easy to effectuate.
Another object is to provide an infusion pump which protects the chemical and medical integrity of infusor liquids.
Another object is to provide an infusion pump which does not extend axially when in use.
These and other objects and advantages will become apparent from the foregoing and ongoing written specifications, the drawings, and the appended claims.